In transport systems for handling mail or other flat articles, there is frequently a need to provide one or more diverter stations, with some of the articles passing through the station undiverted and selected articles being diverted to an alternate transport path or so as to drop into a suitable receptacle at the station. Such diverter stations may, for example, function as sorter stations in a mail handling system.
Such diverters typically utilize a diverter platen or vane over which articles move when the diverter is in a non-divert position. Since in a mail handling system, the articles are normally moving at relatively high speed, the inertia of the articles is generally sufficient to propel them across the diverter without requiring an independent drive on the diverter. However, with no independent drive on the diverter, if the system is turned off for some reason, it is possible for a piece of mail or other article to get hung up on the diverter, creating a jam in the system which must be manually cleared. It is therefore preferable that inertia alone not be relied upon to move articles across the diverter platen.
One solution to this problem is to have the diverter platen be shorter than the articles passing thereacross, or as a minimum of substantially the same length as the shortest article passing thereover, so that by the time the trailing edge of an article leaves the drive mechanism leading into the diverter platen, the leading edge of the article has already been grabbed by the take away mechanism from the platen. However, moderate mail handling systems are required to handle mail pieces which are as small as four or five inches in length, a length shorter than that required for the diverter plate.
A need therefore exists to provide an independent drive for articles passing through a diverter station. However, since the diverter platen itself is preferably a passive platen which performs only the divert function and does not contain a moving drive component, a moving drive component is typically required which would interact with the platen to move articles thereacross. Such a drive component, for example a drive belt, would continue to rotate whether the platen is in its non-divert position where the moving belt/component is used to move articles across the platen or in its tilted, divert position where articles are not driven thereacross. However, in either position, contact between a moving belt/component and a stationary or non-rotating platen would create friction which in turn generates undesired heat in the apparatus, can generate dirt particles as a result of the wear which can interfere with operations of the system and/or stain mail or other articles passing through the apparatus, and most importantly, create wear on both the moving belt/component and the platen, requiring more frequent maintenance and repair for the apparatus, and thus significantly increasing both downtime and operating expense for the system.
While this undesired contact can be eliminated when the platen is in its non-divert position by providing a small spacing between the drive mechanism and platen, in an application such as mail handling where articles as thin as 0.007" must be handled, it is difficult to maintain such close spacing without contact, and this is even more difficult where the articles being handled are of variable thickness, as is generally the case for mail, a typical thickness specification being from 0.007" to 1.25". Such variable thickness pieces are better handled by a biased pinch roller, the bias force being such that the space between the rollers automatically adjusts to handle variable thickness pieces.
One way in which the above problem of handling thin articles, while avoiding contact between the moving component and the platen, might be dealt with is to have the moving component be for example part of a vacuum head spaced a short distance from the platen, the vacuum permitting thin articles to be moved across the divert station without requiring physical contact between the moving component and the platen. However, vacuum is not available at all locations where article sorting is to occur and, even where available, there is frequently limited availability of vacuum. A vacuum head is also more expensive than a moving belt or other component not requiring vacuum and vacuum heads also require more maintenance. Therefore, use of a vacuum head for this application is undesirable. A diverter having an independent drive which meets the performance requirements indicated above without providing friction contact between a moving and stationery surface has not heretofore existed in the art.